Automatic carburetor choke control



July 6, 1937. J. w. r-'rrz GERALD 286,023

AUTOMATIC CRBURETOR CHOKE CONTROL l A Filed Dec. 8, 1934 f@ 4- L72757347MIE/25575@ /Ww Patented July 6, 1937 p UNITED STATES PATENT OFFICEAUTOMATIC CARBURETOR CHOKE CONTROL Application December 8, 1934, SerialNo. 756,629.

15 claims. (01.123-119) This invention relates to improvements inautomatic controls for carburetor choke valves and and has an object toprovide novel means for both `closing and eiecting the re-opening of achoke valve in response to differential in fluid pressure created by theengine.

More speciiically it is an object of this invention to provide a controlfor choke valves which is actuated to close the valve by engine suctionor other fluid pressure prevalent during the cranking of the engine andoperable in response to an increase in the same fluid pressure as theengine starts to operate under its own power for effecting the openingof the choke valve.

Another object of this invention is to provide a control forautomatically closing and opening the choke valve of a carburetorwherein closure of the valve is effected by a low engine suction andwherein the valve is held in its open position during the normal runningconditions of the engine to prevent closure ofthe choke valve wheneverthe suction drops momentarily as in accelerating the engine.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly dened by the appended claims, it beingunderstood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised lfor the practical application of the principlesthereof, and in which:

Figure 1 is a side view showing part of a conventional internalcombustion engine and illustrating the application of this inventionthereto;

Figure 2 is an enlarged longitudinal section view through thecontrolling device taken on the plane of the line 2 2 of Figure 1;

Figure 3 is a cross section view taken through Figure 1 on the plane ofthe line 3 3; and

Figure 4 is a view similar to Figure 2, but with parts thereof inelevation and showing the elements of the control in another position.

Referring now more particularly to the accompanying drawing in whichlike numerals indicate like parts throughout the several views, thenumeral 4 designates the intake manifoldof an internal combustion engine5. A riser 6 forming part of the intake manifold mounts a carburetor l.

The carburetor 1, as is customary, has a fuel line 8 leading to it andan air inlet 9 controlled by a choke valve IIJ. As is well known, bycontrolling the admission of air entering the inlet 9, the fuel-airratio of the fuel mixture is determined, and in starting, it iscustomary to close the choke valve so that a rich mixture will be drawninto the intake manifold.

Heretofore, many diierent means have been provided for controlling thechoke valve automatically so that the broad provision of an automaticcontrol for choke valves is not new. The present invention, however,provides automatic control for the choke valve in a new and novel mannercharacterized by the fact that the same medium which effects closure ofthe valve in starting also eiects the opening of the valve after theengine has attained normal running conditions.

For this purpose, the control of this invention comprises a cylinder IIopen at one end and closed at its other end, except for a small airbleed I2 passing through the end wall I3 of the cylinder.

Operating in the bore I4 of the cylinder is a piston I5 from which anarm I6 projects outwardly-of the open end of the cylinder. The arm I6 isconnected by a link I1 to a crank arm IB fixed to the shaft of the chokevalve I0.

The cylinder II is so mounted with respect to the location of the chokevalve and the length of the link Il that when the piston I5 is in itsinnermost position shown in Figure 2, the choke valve I0 is in its fullyclosed position shown in full lines in Figure 1, and when the piston islin its outermost position, as illustrated in Figure 4, the choke valveis fully'open as indicated in dotted lines in Figure 1.

An expansion spring I9 confined between the end wall I3 of the cylinderand the piston which may be cup shaped so as to embrace the spring,yieldingly urges the piston to its outermost position to normally holdthe choke valve open.

To draw the piston I5 to its innermost position and thereby effectclosure of the choke valve, the closedend of the cylinder iscommunicated through a duct 20 With the intake manifold 4.

As shown in Figures 2 and 4, the duct 2l) is connected to the cylinderII in communication with a port 2| which opens to a. transverse bore 22in the end Wall I3 of the cylinder intersecting the bleed opening I2.

Between the bleed opening I2 and the port 2I, the transverse bore 22 iscommunicated with the interior of the cylinder through a port or passage23. Slidably disposed within the transverse bore 22 is a plunger 24yieldingly urged away from the port 2| by an expansion spring 25. 'Iheaction of the spring 25 is opposed by a thermostat in the form of abimetallic strip 26 anchored to the body of the cylinder II as at 21with its free end bearing against the outer end of the plunger 24.

Being thermally responsive, the bimetallic strip 26 determines theposition of the plunger 24 in accordance with the ambient temperature ofthe strip, and inasmuch as the controlling unit is mounted in closeproximity to the exhaust manifold 28 or a portion thereof, it followsthat the controlling effect of the bimetallic strip 26 and consequentlythe position of the plunger 24 is dependent upon the thermal conditionof the engine.

When the engine is cold, as in starting, the bimetallic strip 26 isflexed outwardly as shown in Figure 2 so that the plunger 24 is held byits spring 25 in a position allowing unrestricted communication betweenthe interior of the cylinder and the intake manifold and at which across bore 30 in the plunger is out of line with the air bleed I2.Consequently, during the cranking of the engine, the suction within theintake manifold exerts an effect on the piston I5 which being ofcomparatively large diameter is acted upon by the relatively slightsuction prevalent during cranking and is drawn to its innermost positionto close the choke valve.

When the engine starts and begins to operate under its own power, theeffect of suction within the intake manifold increases considerably. Theeffect of the increased engine suction now draws the plunger 24 inwardlyagainst the action of its spring 25 to cover the passage I9 shutting offthe cylinder from the intake manifold and disposing the cross bore 30 inthe plunger in line with the air bleed I2 so that the piston I5 is freeto be projected outwardly by its spring I9.

The inward motion of the plunger 24 in response to the increased enginesuction is limited to properly align its cross bore 30 with the airbleed I2, by the engagement of a reduced inner end portion 3| with thebottom of the transverse bore 22 as shown in Figure 4.

Upon release of the piston I 5 from the effect of engine suction, it isprojected outwardly as hereinbefore stated, by its spring I9. Theoutward projection of the piston I5 and consequently the position of thechoke valve I0, however, is furiher controlled in accordance with thethermal conditions of the engine by means of a substantially hairpinshaped bimetallic strip 33 having one end anchored as at 34 and itsother free end engaging one edge of the arm I6 which is provided with aseries of steps 35.

The steps 35 are so disposed that the risers therebetween afford abruptshoulders or abutments successively farther out from the axis of thecylinder so that as the free end of the bimetallic strip 33 movesoutwardly the piston is permitted to move outwardly under the influenceof its spring I9 to progressively close the choke.

The disposition of the metals of the bimetallic strip 33 is such thatits free end moves outwardly as the ambient temperature rises. Hence,the opening of the choke is regulated in accordance with the thermalconditions of the engine, being permitted to open fully only when theengine has attained a normal operating temperature.

The device of this invention also provides for the sudden enrichment ofthe fuel mixture during acceleration as long as the engine is cold, assudden acceleration is accompanied by a decrease in engine suction. -Ifthis occurs while the engine is still cold and the thermostaticcontrolling strip 26 is still flexed outwardly as shown in Figure 2, itfollows that the plunger 24 will be moved outwardly by its spring 25allowing engine suction to again act on the piston I5 and draw the sameinwardly to fully close the choke valve from whatever position it isheld by the thermostat 33.

Obviously after the engine warms up and the controlling thermostat 26straightens out as shown in Figure 4, the loss in engine suction as aresult of acceleration has no effect upon the choke valve as the plunger24 is then held in its innermost position.

From the foregoing description taken in connection with the accompanyingdrawing, it will be readily apparent to those skilled in the art towhich this invention appertains, that this invention affords novel meansfor automatically controlling the position of the choke valve of aninternal combustion engine carburetor, and that the same medium which isutilized to effect closure of the valve is also utilized to effect theopening thereof.

What I claim as my invention is:

1. In combination with an internal combustion engine having a carburetorand a normally open choke valve for controlling the admission of airinto the carburetor, an automatic control for the choke valve comprisingfluid pressure responsive means operable upon a differential in fluidpressure created by the engine during cranking f the engine for closingthe choke valve, and another fluid pressure responsive means operable bya greater differential in said fluid pressure created by the engineduring operation thereof under its own power operable to disconnect saidflrst mentioned fluid pressure responsive means from the source ofpressure differential whereby the choke valve is completely freed fromthe holding effect of said first mentioned fluid pressure responsivemeans.

2. In combination with an internal combustion engine having a carburetorprovided with a choke valve for controlling the admission of air intothe carburetor, means for yieldingly urging the choke valve toward openposition, and an automatic control for closing the choke valve duringstarting of the engine comprising a member connected with the valve andmovable to close the same, fluid pressure responsive means for movingsaid member upon a predetermined differential in fluid pressure createdby the engine during cranking, and another fluid pressure responsivemeans operable upon an increased differential in said fluid pressureresulting from operation of the engine under its own power operable todisconnect said first named fluid pressure responsive means from thesource of pressure differential whereby the choke valve is completelfreed from the holding effect of said first mentioned fluid pressureresponsive means so that the choke valve is moved toward open positionby the yieldable means as the engine begins to operate under its ownpower.

3. In combination With an internal combustion engine having a carburetorand a normally open choke valve for controlling the admission of air lliinto the carburetor, means responsive to fluid pressure created by theengine during cranking thereof for closing the choke valve, and meansresponsive to fluid pressure created by the engine when the same isrunning under its own power for disconnecting said first mentioned fluidpressure responsive means from the effect of the fluid pressure.

4. In combination with an internal combustion engine having an intakemanifold and a carburetor having a normally open choke valve forcontrolling the admission of air into the carburetor, means operable bysuction created within the intake manifold by the engine during crankingfor closing the choke valve, and means operable by the greater suctionwithin the intake manifold created by the engine during operationthereof under its own power for disconnecting said first mentionedsuction operated means from the source of suction.

5. In combination with an internal combustion engine having a closedsystem within which a partial vacuum is created by the engine and acarburetor provided with a choke valve for controlling the admission ofair into the carburetor, yielding means for holding the choke valveopen, means responsive to the effect of suction within said closedsystem during cranking of the engine for closing the choke valve, andmeans responsive to the effect of greater suction within said closedsystem during the running condition of the engine for disconnecting saidfirst named suction responsive means from the source of suction.

6. In combination with an internal combustion engine having a closedsystem within which a partial vacuum is created by the engine and acarburetor provided with a choke valve for controlling the admission ofair into the carburetor, yielding means for holding the choke valveopen, means responsive to the effect of suction within said closedsystem during cranking of the engine for closing the choke valve, meansresponsive to the effect of greater suction within said closed systemduring the running condition of the engine for rendering said firstnamed suction responsive means ineffective to hold the choke valve open,and thermally responsive means for holding said last named suctionoperated means in its operative position regardless of decrease inengine suction as long as a predetermined temperature condition obtainsat said thermally responsive means, whereby closure of the choke valveafter the engine is operating normally and has reached normal operatingtemperature is prevented.

'7. In combination with an internal combustion engine having meanswithin which the engine creates a partial vacuum and having a carburetorprovided with a choke valve for controlling the admission of air intothe carburetor, yielding means for holding the choke valve open, acylinder, a piston operating in the cylinder, means connecting thepiston with the choke valve, means for communicating the cylinder withthe means in which the engine creates a partial vacuum so that upon theestablishment of a partial vacuum within said means during cranking ofthe engine the piston is moved to a position closing the choke valve,and means responsive to a higher vacuum created within said means by theengine operating under its own power for closing off communicationbetween the cylinder and said means within which a vacuum is created torender said piston ineffective to hold the choke valve closed.

8. In combination with an internal combustion engine having means tocreate a fluid pressure differential and having a carburetor providedwith a choke valve to control the admission of air into the carburetor,means for controlling the choke valve from variations in pressuredifferential, comprising a cylinder having a port through which theeffect of fluid pressure differentials created by the engine aremanifested within the interior of the cylinder, a piston operating inthe cylinder in response to such fluid pressure differential, aconnection between the piston and the choke valve whereby actuation ofthe piston in one direction closes the choke valve,

yielding means for opposing the motion of the? piston in response tofluid pressure differential and for normally holding the choke valveopenjr a second cylinder in which the effect of the same fluid pressuredifferential is manifested, a second piston operating in said secondcylinder, said second piston being adapted for closing the port of thefirst mentioned cylinder and being responsive only to a greater pressuredifferential than that at which the rst mentioned piston respondswhereby the first piston acts to close the choke valve in response tolow fiuid pressure differentials prevalent during cranking of the engineand the second piston acts to render the first mentioned pistonineffective to hold the choke valve closed upon the attainment of ahight' er fluid pressure differential as a result of the engineoperating under its own power.

9. In combination with an internal combustion engine having means forcreating a fluid pressure differential and a carburetor provided with achoke valve for controlling the admission of air into the carburetor, anautomatic control for the choke valve comprising a cylinder providedwith a port through which the effect of the fluid pressure differentialcreated by the engine is introduced to the, interior of the cylinder, apiston operating in the cylinder and responsive to a fluid pressuredifferential prevalent during cranking of the engine, a connectionbetween said piston and the choke valve whereby response of the pistoncloses the choke Valve during cranking of the engine, and meansresponsive to a higher fluid pressure differential obtained duringnormal running of the engine for closing said port to release the pistonfrom the effect of the fiuid 1 pressure differential, and means foryieldingly urging the choke valve toward open position at all times sothat upon release of the piston from the effect of the fluid pressuredifferential the choke valve is moved toward open position.

10. In combination with an internal combustion engine having means forcreating a fluid pressure differential and a carburetor provided with achoke valve for controlling the admission of air into the carburetor, anautomatic control for the choke valve comprising a cylinder, aconnection leading to the cylinder through which the effect of a fluidpressure differential created by the engine ismanifested within thecylinder, a piston operating in the cylinder and responsive to a lowfluid pressure differential established within the cylinder, meansconnecting the piston with the choke valve whereby response of the.piston closes the choke valve, a second cylinder, means connected withthe second cylinder through which the effect of the fluid pressuredifferential created by the engine is manifested within said secondcylinder, a piston operating in the second cylinder and responsive to ahigh fluid pressure differential for movement to a position shutting offthe first mentioned cylinder from the effect of the fluid pressuredifferential to thereby release the first mentioned piston for movementto a position allowing opening of the choke valve, and spring means toyieldingly urge the choke valve toward open position.

11. In a device of the character described, a cylinder, a piston in saidcylinder, the cylinder having a port through which a fluid preessuredifferential at opposite sides of the piston may be established formoving the piston in one direction, a spring yieldingly urging thepiston in a direction opposite the direction of motion of the piston inresponse to the liuid pressure differential at opposite sides of thepiston, another cylinder of smaller cross sectional area than the firstmentioned cylinder, and another piston operating in said other cylinder,said other cylinder having means through which a fluid pressuredifferential may be established at opposite sides of said other pistonso that said other piston is movable in response to a higher fluidpressure differential than that at which the first piston operates to aposition closing said port whereby the first mentioned cylinder is shutoff from the effect of fluid pressure so that the first mentioned pistonis free to be operated by its spring.

l2. In a device of the character described, a cylinder open at one endand having an end wall closing its opposite end, said end wall having anair bleed for communicating the closed end portion of the cylinder withthe atmosphere and having a port through which uid pressure may beintroduced into the interior of the cylinder, a piston operating in thecylinder and movable in one direction by fluid pressure introduced intothe cylinder through said port, a spring to oppose such motion of thepiston, a second cylinder provided by a bore in the end wallintersecting the air bleed and communicating with said port so that saidsecond cylinder is subjected to the same fluid pressure as the firstcylinder, and a piston operating in said second cylinder and movable inresponse to a predetermined fluid pressure in said second cylinder to aposition closing the port leading to the first mentioned cylinder andopening the air bleed, whereby the first mentioned piston is releasedfor actuation by its spring means.

13. In combination with an internal combustion engine having an intakemanifold within which the engine creates a partial vacuum and acarburetor provided with a choke valve adapted for controlling theadmission of air into the carburetor, an automatic control for the chokevalve comprising a cylinder provided with an end wall, said end wallhaving an air bleed for communicating the interior of the cylinder withthe atmosphere and having a port communicating with the interior of thecylinder, said end wall also having a bore intersecting said air bleedand communicating with said port, said bore providing a second cylinder,means for communicating said bore with the intake manifold whereby bothcylinders are subjected to the effect of vacuum Within the intakemanifold, a piston operating in the first cylinder in response to lowvacuum, means connecting said piston with the choke valve so thatresponse of Said piston to low vacuum closes the choke valve, means toyieldingly urge the choke valve toward open position. a second pistonoperating in the second cylinder and biased to a position closing theair bleed and allowing unrestricted communication between the port andsaid second cylinder, said second cylinder and the second pistonoperating therein being of smaller cross sectional area than the firstcylinder and piston so as to respond only to a higher vacuum in theintake manifold, and saidsecond piston moving in response to a highervacuum to a'position closing said port and opening the air bleed,whereby the first designated piston is free from the effect of vacuumfor actuation by its yieldable urging means.

14. In combination with an internal combustion engine having an intakemanifold within which the engine creates a partial vacuum and acarburetor provided with a choke valve adapted for controlling theadmission of air into the carburetor, an automatic control for the chokevalve comprising a cylinder provided with an end wall, said end wallhaving an air bleed for communieating the interior of the cylinder withthe atmosphere and having a port communicating with the interior of thecylinder, said end wall .also having a bore intersecting said air bleedand communicating with said port, said bore providing a second cylinder,means for communicating said bore with the intake manifold whereby bothcylinders are subjected to the effect of vacuum within the intakemanifold, a piston operating in the first cylinder in response to lowvacuum, means connecting said piston with the choke valve so thatresponse of said piston to low vacuum closes the choke valve, means toyieldingly urge the choke valve toward open position, a second pistonoperating in the second cylinder and biased to a position closing theair bleed and allowing unrestricted communication between the port andsaid second cylinder, said second cylinder and the second pistonoperating therein being of smaller cross sectional area than the firstcylinder and piston so as to respond only to a higher vacuum in theintake manifold, and said second piston moving in response to a highervacuum to a position closing said port and opening the air bleed,whereby the first designated piston is free from the effect of vacuumfor actuation by its yieldable urging means, and thermostatic means tocontrol the opening of the choke valve upon release of the firstdesignated piston from the effect of vacuum.

15. In combination with an internal combustion engine having an intakemanifold within which the engine creates a partial vacuum and a rcarburetor provided with a choke valve adapted for controlling theadmission of air into the carburetor, an automatic control for the chokevalve comprising a cylinder provided with an end wall, said end Wallhaving an air bleedfor communicating the interior of the cylinder withthe atmosphere and having a port communicating with the interior of thecylinder, said end wall also having a bore intersecting said air bleedand communicating with said port, said bore providing a secondcyclinder, means for communicating said bore with the intake manifoldWhereby both cylinders are subjected to the effect of vacuum Within theintake manifold, a piston operating in the first cylinder in response tolow vacuum, means connecting said piston with the choke valve so thatresponse of said piston to low vacuum closes the choke valve, means toyieldingly urge the choke valve toward open position, a second pistonoperating in the second cylinder and biased to a position closing theair bleed and allowing unrestricted communication between the port andsaid second cylinder, said second cylinder and the second pistonoperating therein being of smaller cross sectional area than the rstcylinder and piston so as to respond only to a higher vacuum in theintake manifold, and said second piston moving in response to a. highervacuum to a position closing said port and opening the air bleed,whereby the rst designated piston is free from the effect of vacuum foractuation by its yieldabie urging means, and thermostatic means operableupon the attainment of a predetermined ambient temperature for holdingthe second designated piston in its position to which it moves inresponse to vacuum.

JOHN W. Fl'rz GERALD,

